Cathodic corrosion protection system with rebar mounting assembly

Abstract

In a method for cathodically protecting and/or passivating a metal section in an ionically conductive material such as steel reinforcement in concrete or mortar, an impressed current or sacrificial anode is mounted on the metal reinforcing bar by attaching a nut member having a female thread to the metal reinforcing bar by elongate flexible wires attached to the nut member so that the nut member and wires encircle the metal reinforcing bar and rotating a threaded rod member carrying the anode body into the female thread so that a forward end of the rod member engages with a front face of the metal reinforcing bar and pulls on the nut member away from the metal reinforcing bar to tension the wrapping wires.

Claims

1. An anode assembly for use in cathodically protecting and/or passivating a metal reinforcing bar in an ionically conductive material, comprising: an anode body for mounting at least partly within the ionically conductive material for communication of an ionic current through the ionically conductive material to the metal reinforcing bar; the anode body being constructed and arranged so that when ionically connected to the ionically conductive material a voltage difference is generated between the anode body and the metal reinforcing bar so as to cause a current to flow through the ionically conductive material between the anode body and the metal reinforcing bar so as to provide cathodic protection of the metal reinforcing bar; and a mounting assembly for fixedly mounting the anode body on the metal reinforcing bar so as to be supported by the bar within the ionically conductive material; the mounting assembly comprising: a threaded rod member extending forwardly from the anode body to a forward end of the rod member arranged for engagement with a front face of the metal reinforcing bar; a nut member having a female thread for engagement onto the threaded rod with the forward end of the rod member projecting forwardly of the nut member; at least one elongate flexible wrapping member arranged to be attached to the nut member; the nut member and the flexible wrapping member being arranged to encircle the metal reinforcing bar to attach the nut member to the metal reinforcing bar.

2. The anode assembly according to claim 1 wherein the anode body is attached to the threaded rod member so that manual rotation of the anode body drives rotation of the forward end of the threaded rod member into the female thread.

3. The anode assembly according to claim 1 wherein the forward end of the threaded rod member includes one or more projections for biting into the bar.

4. The anode assembly according to claim 1 wherein the threaded rod member is rigidly coupled to the anode body to fixedly hold the anode body at a predetermined distance and orientation relative to the bar.

5. The anode assembly according to claim 1 wherein said at least one elongate flexible wrapping member comprises at least two wire portions attached to the nut member and arranged to be wrapped around the metal reinforcing bar and twisted together.

6. The anode assembly according to claim 5 wherein one wire portion is attached to the nut member so as to extend outwardly from one side of the female thread and the other wire portion is attached to the nut member as to extend outwardly from an opposed side of the female thread allowing the wire portions to be wrapped around the metal reinforcing bar in opposite directions and twisted together.

7. The anode assembly according to claim 5 wherein first and second wire portions are attached to the nut member so as to extend outwardly from one side of the female thread and third and fourth wire portions attached to the nut member as to extend outwardly from an opposed side of the female thread.

8. The anode assembly according to claim 7 wherein said first and second wire portions are mounted on the nut member so as to be spaced along the metal reinforcing bar from said third and fourth wire portions.

9. The anode assembly according to claim 1 wherein said at least one elongate flexible wrapping member comprises a strap arranged to be wrapped around the metal reinforcing bar and fastened to the nut.

10. An anode assembly for use in cathodically protecting and/or passivating a metal reinforcing bar in an ionically conductive material, comprising: an anode body for mounting at least partly within the ionically conductive material for communication of an ionic current through the ionically conductive material to the metal reinforcing bar; the anode body being constructed and arranged so that when ionically connected to the ionically conductive material a voltage difference is generated between the anode body and the metal reinforcing bar so as to cause a current to flow through the ionically conductive material between the anode body and the metal reinforcing bar so as to provide cathodic protection of the metal reinforcing bar; and a mounting assembly for fixedly mounting the anode body on the metal reinforcing bar so as to be supported by the bar within the ionically conductive material; the mounting assembly comprising: a threaded rod member extending forwardly from the anode body to a forward end of the rod member arranged for engagement with an adjacent face of the metal reinforcing bar; a nut member having a female thread for engagement onto the threaded rod with the forward end of the rod member projecting forwardly of the nut member; and at least two wire portions attached to the nut member and arranged to be wrapped around the metal reinforcing bar and twisted together.

11. The anode assembly according to claim 10 wherein one wire portion is attached to the nut member so as to extend outwardly from one side of the female thread and the other wire portion is attached to the nut member as to extend outwardly from an opposed side of the female thread allowing the wire portions to be wrapped around the metal reinforcing bar in opposite directions and twisted together.

12. The anode assembly according to claim 10 wherein first and second wire portions are attached to the nut member so as to extend outwardly from one side of the female thread and third and fourth wire portions attached to the nut member as to extend outwardly from an opposed side of the female thread.

13. The anode assembly according to claim 12 wherein said first and second wire portions are mounted on the nut member so as to be spaced longitudinally of the metal reinforcing bar from said third and fourth wire portions.

14. An anode assembly for use in cathodically protecting and/or passivating a metal reinforcing bar in an ionically conductive material, comprising: an anode body for mounting at least partly within the ionically conductive material for communication of an ionic current through the ionically conductive material to the metal reinforcing bar; the anode body being constructed and arranged so that when ionically connected to the ionically conductive material a voltage difference is generated between the anode body and the metal reinforcing bar so as to cause a current to flow through the ionically conductive material between the anode body and the metal reinforcing bar so as to provide cathodic protection of the metal reinforcing bar; and a mounting assembly for fixedly mounting the anode body on the metal reinforcing bar so as to be supported by the bar within the ionically conductive material; the mounting assembly comprising: a threaded rod member extending forwardly from the anode body to a forward end of the rod member arranged for engagement with a front face of the metal reinforcing bar; a nut member having a female thread for engagement onto the threaded rod with the forward end of the rod member projecting forwardly of the nut member; the nut member having on each side of the female thread a receptacle for receiving a respective portion of at least one elongate flexible wrapping member arranged to be attached to the nut member to encircle the metal reinforcing bar to attach the nut member to the metal reinforcing bar.

15. A method for cathodically protecting and/or passivating a metal reinforcing bar in an ionically conductive material, comprising: providing an anode body comprising an anode for communication of an ionic current through the ionically conductive material to the metal reinforcing bar, the anode body being constructed and arranged so that when the anode is ionically connected to the ionically conductive material a voltage difference is generated between the anode and the metal reinforcing bar so as to cause a current to flow through the ionically conductive material between the anode and the metal reinforcing bar so as to provide cathodic protection of the metal reinforcing bar; and mounting the anode body on the metal reinforcing bar by: attaching a nut member having a female thread to the metal reinforcing bar by at least one elongate flexible wrapping member so that the nut member and wrapping member encircle the metal reinforcing bar; and rotating a threaded rod member into the female thread so that a forward end of the rod member engages with a front face of the metal reinforcing bar and pulls on the nut member away from the metal reinforcing bar to tension said at least one wrapping member; the anode body being carried on the threaded rod member.

16. The method according to claim 15 wherein the threaded rod member is driven in rotation by rotating the anode body.

17. The method according to claim 15 wherein the forward end of the threaded rod member includes one or more projections which bite into the bar.

18. The method according to claim 15 wherein the anode body is rigidly coupled to the threaded rod member and fixedly held at a predetermined distance and orientation relative to the bar.

19. The method according to claim 15 wherein said at least one elongate flexible wrapping member comprises at least two wire portions which attached to the nut member and which are wrapped around a rear face of the metal reinforcing bar and twisted together at the front face.

20. The method according to claim 19 wherein one wire portion is attached to the nut member so as to extend outwardly from one side of the female thread and the other wire portion is attached to the nut member as to extend outwardly from an opposed side of the female thread allowing the wire portions to be wrapped around the metal reinforcing bar in opposite directions and twisted together at the front face.

21. The method according to claim 19 wherein first and second wire portions are attached to the nut member so as to extend outwardly from one side of the female thread and third and fourth wire portions attached to the nut member as to extend outwardly from an opposed side of the female thread, said first and second wire portions are mounted on the nut member so as to be spaced along the metal reinforcing bar from said third and fourth wire portions, wrapping the wire portions around the metal reinforcing bar and twisting together the first and third wire portions on one part of the metal reinforcing bar and together the second and fourth wire portions on another part of the metal reinforcing bar spaced along the reinforcing bar.

22. The method according to claim 15 wherein said at least one elongate flexible wrapping member is separate from the nut member for attachment thereto.

23. The method according to claim 22 wherein the nut member includes first and second receptacles each on a respective side of the female thread for attachment thereto of the separate wrapping member.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the invention will now be described in conjunction with the accompanying drawings in which:

(2) FIG. 1 is a cross-sectional view of an anode assembly including a mounting method for attachment of the anode body to the reinforcing bar according to the present invention.

(3) FIG. 2 is an enlarged view of the mounting of the anode body of FIG. 1.

(4) FIG. 3 is a top plan view of the nut member and wrapping wires of the mounting of FIG. 1.

(5) FIG. 4 is an enlarged view of the mounting of FIG. 1 taken as a cross-section transverse to the reinforcing bar.

(6) FIG. 5 is a side elevational view of the mounting of FIG. 4.

(7) FIG. 6 is a cross-sectional view of an anode assembly including a further embodiment of a mounting method for attachment of the anode body to the reinforcing bar according to the present invention.

(8) FIG. 7 is an isometric view of the arrangement of FIG. 7.

(9) FIG. 8 is a top plan view of the nut member and wrapping wires of an alternative embodiment of the mounting of FIG. 1 which uses cable ties.

(10) FIG. 9 is a side elevational view of the mounting of FIG. 7.

(11) In the drawings like characters of reference indicate corresponding parts in the different figures.

DETAILED DESCRIPTION

(12) In the example shown in FIG. 1 there is provided a cell which may be rechargeable or may be a simple non-rechargeable cell. The cell may form part of the anode structure or the anode and the cell may be physically separated. As shown in FIG. 1, an anode body 10 is defined by a typical alkaline manganese dioxide-zinc rechargeable cell comprises the following main units: a steel can 12 defining a cylindrical inner space, a manganese dioxide cathode 14 formed by a plurality of hollow cylindrical pellets 16 pressed in the can, a zinc anode 18 made of an anode gel and arranged in the hollow interior of the cathode 14, and a cylindrical separator 20 separating the anode 18 from the cathode 14. The ionic conductivity (electrolyte) between the anode and the cathode is provided by the presence of potassium hydroxide, KOH, electrolyte added into the cell in a predetermined quantity. Other types of rechargeable cells comprise similar main components (can, cathode, anode, separator and electrolyte) but the composition of the components may differ. Some of the types of cell may however be of a different construction such as lead/acid cells or lithium cells.

(13) The can 12 is closed at the bottom, and it has a central circular pip 22 serving as the positive terminal. The upper end of the can 12 is hermetically sealed by a cell closure assembly which comprises a negative cap 24 formed by a thin metal sheet, a current collector nail 26 attached to the negative cap 24 and penetrating deeply into the anode gel to provide electrical contact with the anode, and a plastic top 28 electrically insulating the negative cap 24 from the can 12 and separating gas spaces formed beyond the cathode and anode structures, respectively.

(14) The material of separator 20 consists of two different materials, i.e.: a first material 30 made of fibrous sheet material wettable by the electrolyte, and a second material 32 being impermeable to small particles but retaining ionic permeability. An expedient material for the first layer is a sheet material of non-woven polyamide fiber, which is absorbent and serves as a reservoir for electrolyte. The macro-porous structure of the absorbent layer cannot prevent internal shorting by zinc dendrites or deposits during discharge/charge cycling.

(15) Shorting is prevented by the second 32 material which may be a layer or layers of micro-porous or non-porous material which may be laminated to or coated onto the fibrous sheet material. One suitable material is one or more cellophane membranes laminated to the non-woven polyamide sheet. Another is one or more coatings of regenerated cellulose or viscose coated onto and partially impregnating the non-woven polyamide sheet, resulting in a composite material.

(16) Other types of rechargeable cells may be used. In the present arrangement, the type described above is used in a method for cathodically protecting and/or passivating a metal section such as steel reinforcing bar 40 in an ionically conductive material such as concrete 41. The cell therefore includes a first terminal 42 and a second terminal 43 defined by the outer casing 12. The first terminal 42 is connected to the pin or nail 26 which is engaged into the anode material 18. The terminal 42 connects to a connecting wire 42A which extends from the terminal 42 for eventual connection to the steel reinforcing bar 40 as shown in FIG. 1 through the mounting assembly generally indicated at 50 which mechanically and electrically attaches the anode body to the bar 40.

(17) In FIG. 1, an anode 44 is applied as a coating onto the casing 12 of the cell. In this embodiment the anode 44 is of an inert material so that it is more noble than steel. Examples of such materials are well known. Thus the anode material 44 does not corrode or significantly corrode during the cathodic protection process.

(18) In this arrangement the application of the anode 44 onto the outside surface of the casing 12 provides the structure as a common single unit where the anode is directly connected to the cell and forms an integral element with the cell. Anode 44 may comprise one or more layers and may include a mixed metal oxide (MMO), catalytic or sub-oxide layer.

(19) In this embodiment, as the anode 44 is formed of an inert material which does not corrode in the protection process, the anode and the cell contained therein can be directly incorporated or buried in the concrete or other ionically conductive material without the necessity for an intervening encapsulating material such as a porous mortar matrix. As there are no corrosion products there is no requirement to absorb such products or the expansive forces generated thereby. As the process does not depend upon continued corrosion of a sacrificial anode, there is no necessity for activators at the surface of the anode. As the chemical reaction at the surface of any inert anode during operation generates acid (or consumes alkali) it is beneficial for the anode to be buried in an alkaline material such as concrete or high alkalinity mortar to prevent material near the anode from becoming acidic. If desired, additional alkali may be added to the concrete or other material the anode is in contact with.

(20) The apparatus shown herein includes an anode body generally indicated at 10 which is connected to the reinforcing bar 40 by the mounting assembly generally indicated at 50. In addition, the anode body includes a current limiting system generally indicated at 51 which limits the flow of current from the anode body to the bar 40, which is not part of the present invention.

(21) As previously described, the anode body can be defined by a power supply typically in the form of a cell with the anode 44 on the outside surface of the cell and with the other terminal of the cell provided at the end of the cell for connection to the bar 40.

(22) In other embodiments described hereinafter the cell can be omitted in which case the anode body comprises a sacrificial material which is less noble than the steel rebar, such as zinc where a voltage between the anode and the bar comprises the galvanic voltage between the two metal components.

(23) In yet another embodiment, the anode body can comprise a combination of both an impressed current anode and a sacrificial anode.

(24) In this way the anode body is constructed and arranged so that when the anode is ionically connected to the concrete, a voltage difference is generated between the anode 44 and the bar 40 so as to cause a current to flow through the concrete between the anode and the bar 40 so to provide cathodic protection and/or passivation of the reinforcing bar in the concrete.

(25) In the embodiment shown in FIGS. 1, 3 and 4, the mounting assembly 50 comprises a threaded rod 53 which is attached at one end to the anode body 10. An opposed end 54 of the threaded rod forms a front face for engaging one side face of the bar 40. As shown in FIGS. 2 and 4, the end face 54 of the threaded rod 53 includes a peripheral circular edge 55 and intervening projections 56 which are arranged to bite into the surface of the bar 40 when in compressed contact therewith.

(26) The mounting assembly 50 further comprises wrapping member 60 for engaging generally the opposed the face of the bar 40 at a surface 58. In general the wrapping member 60 contacts the opposite or rear surface of the bar 40 at least at two positions and on either side of a diameter extending through the bar 40 from the face 54. In this way the bar 40 is contacted by the front face 54 and the inside surface of the wrapping member 60 to provide a stable engagement.

(27) In this embodiment a female threaded portion 61 is provided by a threaded hole through a nut member 62. A screw action pulling the nut member 62 member toward the anode body is therefore provided by rotating the rod 53. This can most effectively be done by grasping manually the anode body and using it as a handle to turn the rod 53. Of course this requires a strong connection between the bottom end of the rod 53 and the anode body. In the arrangement shown in FIG. 2, this connection is provided by a base plate 71 attached onto the bottom end of the rod 53 and engaged firmly into the upper end of the anode body. In an arrangement using a solid anode of a sacrificial material, the rod 53 can be cast into the interior of the anode body to provide the necessary structural and electrical connection.

(28) The mounting assembly for fixedly mounting the anode body 10 on the metal reinforcing bar 40 so as to be supported by the bar within the ionically conductive material includes the threaded rod 53, the nut member 62 with the female thread 61 and the wrapping member 60.

(29) The threaded rod member 53 extends forwardly from the anode body 10 to the forward end 54 of the rod member 53 arranged for engagement with a front face 401 of the metal reinforcing bar 40. The nut member 62 has the female thread 61 extending therethrough so that the thread forms an open end for insertion of the rod 53 and a second open end at the bar so that the front face can project through the open end for engagement onto the reinforcing bar.

(30) The nut member 62 in this embodiment is connected to at least one elongate flexible wrapping member 60 attached to the nut member 62 with the nut member 62 and the attached flexible wrapping member 60 being arranged to encircle the metal reinforcing bar to attach the nut member 62 to the metal reinforcing bar 40.

(31) The nut member comprises a sleeve portion 63 surrounding the rod 53 with a flange or base plate 64 at one end of the sleeve lying in a radial plane of the axis of the rod.

(32) In this embodiment, the elongate flexible wrapping member 60 comprises four wire portions 601, 602, 603 and 604. The portions 601 and 602 form parts of a common wire strip and the portions 603 and 604 form part of a common wire strip. These strips are attached to the nut member and arranged to be wrapped around the metal reinforcing bar 40 and twisted together at a twisted portion 605, 606.

(33) The strips forming the wire portions are attached to the nut member by lying across the underside of the flange 64 with a curved portion 607 wrapped around the sleeve 63 and by being clamped onto the underside of the flange 64 by respective tabs 66, 67 .and 68, 69. Thus the flange 64 which is generally flat is cut at slit lines 76 to form the tabs which are then folded onto the underside of the flange 64 as best shown in FIG. 5 to clamp around the wires strips and hold them against the flange. In this way the wire portions 601 and 603 are clamped to the nut member and extend outwardly from one side 621 of the female thread sleeve 63 and the other wire portion is attached to the nut member as to extend outwardly from an opposed side 622 of the female thread sleeve 63 allowing the wire portions to be wrapped around the metal reinforcing bar 40 in opposite directions to opposite sides 401, 402 of the bar 40 and twisted together at 605, 606.

(34) As shown best in FIGS. 3 and 5, the wire portions 601, 602 are mounted on the nut member 62 so as to be spaced along the metal reinforcing bar at a position 610 from said third and fourth wire portions at a position 611. This holds the nut member stably positioned relative to the front face 54 of the rod 53 since the nut member is pulled toward the bar 40 in both directions to both sides of the rod 53.

(35) In an alternative arrangement shown in FIGS. 6 and 7, an elongate flexible wrapping member 80 for pulling the nut 621 toward the bar 40 comprises a strap 81 arranged to be wrapped around the bar 40 and fastened to the nut.

(36) The strap has a width much greater than the wires so that the single strap sits stably in the bar and pulls symmetrically on the nut. The strap has one end 82 fixedly attached to the nut 621 at top and bottom faces of the nut 621 with holes 83 through which the rod 53 can pass as it is fed through the thread in the nut member. The other end 85 of the strap has a series of holes 86 so that when wrapped around the rod and back to the nut member, the insertion of the rod 53 through the selected one of the holes 86 connects the strap back to the nut member so that they encircle the bar 40.

(37) In the method of use, therefore the arrangement herein allows the nut member 62 to be first attached to the metal reinforcing bar 40 by the elongate flexible wrapping member 60 so that the nut member and wrapping member encircle the metal reinforcing bar and hold the nut member close against the bar 40. Subsequently the rod 53 is inserted and rotated into the female thread so that the forward end of the rod member engages with a front face of the metal reinforcing bar and pulls on the nut member away from the metal reinforcing bar to tension the wrapping member.

(38) In FIGS. 8 and 9 is shown an alternative arrangement which uses cable or zip ties 70 to attach the base plate 641 to the bar 40. The zip ties are of the type which has a strap 71 and a loop 72 which connect and hold the strap at the required tension. This as shown in FIG. 8, the base plate 641 has respective loops or receptacles 642 and 643 on respective sides of the sleeve portion 63 of the nut member 62. The loops form an opening through which the strap of the tie 70 can be passed to attach the tie to the base plate with the loop extending to one side of the bar 40 and the strap to the other side allowing them to be wrapped around and connected either at the rear as shown in FIG. 9 at 701 or at the front as shown at 702. The ties can be attached to the nut member when supplied as shown at 703 which is attached to loop 641 or can be a separate component supplied separately as the ties are of course common, as shown at loop 643.

(39) While the plastic ties are not conductive, the connection can be provided by the front face 54 alone or ties of a conductive material may be used.

(40) While the wires of the previous embodiment are shown attached to the nut member, it is also possible that the wires can be supplied as separate elements for insertion through the loops 641, 643 and wrapped around the bar for twisting together.

(41) Since various modifications can be made in my invention as herein above described, and many apparently widely different embodiments of same may be made within the spirit and scope of the claims without department from such spirit and scope, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.